Individual components of an optical system typically need to be aligned in order for the system to function efficiently. In the case of small components using coherent radiation, such as laser diodes and other semi-conducting optical elements, the alignments need to be of the order of 0.5 μm or better. Passive alignment, wherein components are positioned and are used without further adjustment, is typically unable to achieve this level of alignment. Consequently, active alignment, wherein positions of components are adjusted after initial positioning, with the radiation on, is normally required to complete the alignment process. A number of active alignment systems are known in the art.
U.S. Pat. No. 4,753,510, to Sezerman, whose disclosure is incorporated herein by reference, describes an adjustable connector for coupling a pair of fibre optics. Each optic is removably coupled to a beam expanding lens in a base plate, and the plates are adjusted relative to each other. A level of the signal transmitted between the fibre optics is used to determine when the fibre optics are correctly aligned.
U.S. Pat. No. 4,989,940, to Wollenweber et al., whose disclosure is incorporated herein by reference, describes a system for aligning a fibre optic to a ball lens of a connector. Light from the ball lens is focussed onto a quadrant electrometer, and the fibre optic is adjusted in x, y, and z directions until the output from the quadrants is a minimum.
U.S. Pat. No. 5,253,834, to Sullivan et al., whose disclosure is incorporated herein by reference, describes an alignment fixture having a spherical sector. The spherical surface of the sector rests on a plate, the plate being moved to align a flat surface of the sector. An object for alignment is mounted on the flat surface, and the fixture enables the object to be adjusted in an unobstructed manner.
U.S. Pat. No. 5,937,123, to Frelier, whose disclosure is incorporated herein by reference, describes a fibre optic alignment device. The fibre optic is fed through and bonded to a stainless steel ball. The ball is held in place in the device by springs, which allow the ball to be rotated so that the fibre optic aligns with a lens in the device. After alignment the ball is fixed in place.
U.S. Pat. No. 6,170,795, to Wayne, whose disclosure is incorporated herein by reference, describes a system for aligning a sphere. The sphere contains an optical device, or may at least partially be the optical device. To align the device, the sphere is mounted on balls so that it may be rotated about its center. The multiple ball mounting enables rotation of the sphere about its center, while precluding linear motion of the center.
U.S. Pat. No. 6,430,337, to Bergmann et al., whose disclosure is incorporated herein by reference, describes a system for aligning a light beam generated by a wavelength division multiplexer surface. The system includes an optical wedge which is adjusted until the light beam aligns with a light path through the system.
U.S. Pat. Nos. 6,536,736 and 6,570,721, to Wayne et al., whose disclosures are incorporated herein by reference, describe a sphere which acts as an optomechanical mounting. The sphere is held in place by springs which allow the sphere to rotate about its center, while preventing lateral movement of the center. The sphere may have openings in the sphere for light paths or for tools to adjust the sphere's alignment.
U.S. Pat. No. 6,709,169, to Rossi, whose disclosure is incorporated herein by reference, describes a structure that couples a laser diode to a fibre optic. The structure includes a ball through which the fibre optic penetrates. A tube holds the ball, the laser diode, and a lens coupling the light from the laser diode into the fibre optic. The ball may be rotated and moved within the tube to align the diode and the fibre optic.
U.S. Patent Application 2002/0179792, to Wu et al., whose disclosure is incorporated herein by reference, describes a clamp for a ball with a hole traversing the ball. An optical component is inserted in the hole. The ball is held in the clamp, and may be rotated, without translation, in the clamp, so as to align the component.
U.S. Patent Application 2003/0063870, to Reis, whose disclosure is incorporated herein by reference, describes a micro-assembly which holds a micro-element. The micro-assembly has a rounded portion which contacts a support structure upon which the micro-assembly is mounted. The rounded portion may be translated and rotated relative to the support structure, thereby allowing alignment of the micro-element.
In a publication entitled “A Compact Transmitter and Receiver for 10-Gbit/s Transceiver Modules,” by Kanda et al. published in the proceedings the 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2002, (LEOS 2002) page 606, which is incorporated herein by reference, the authors describe an optical module transmitting collimated light into a fibre optic. A laser diode and a lens are passively aligned in guiding grooves, and the fibre is actively aligned with radiation from the lens.
Notwithstanding the alignment systems presently in use, there is a need for a simple and versatile optical alignment system.